In general, a liquid medicine injection device such as an insulin injection device is used to inject a liquid medicine into a patient's body. Such a liquid medicine injection device is used by medical professionals such as a doctor or a nurse, but it is mostly used by an ordinary person such as a patient himself or a caregiver. In case of diabetic patients, particularly diabetic children, it is necessary to inject liquid medicine such as insulin into a human body at regular intervals. Thus, a patch-type liquid medicine injection device that can be used by being attached to a human body for a predetermined period of time has been researched and developed. Such a liquid medicine injection device may be used while being attached as a patch type to the abdomen or waist of a patient for a predetermined period of time.
In order to be attached to a human body, the liquid medicine injection device needs to be excellent wearable sensation, comfortable to use, excellent in durability, and driven with low power. In addition, for daily life of the patient, the liquid medicine injection device requires an excellent waterproofing function, and a product to be sold needs to remain sterile. However, a conventional liquid medicine injection device cannot satisfy such conditions.